If the Berlin lorry deaths prove to be an act of terrorism it will not come as a shock to the authorities in Britain.

Islamic State has encouraged such attacks by lone wolves even before 86 people were killed in Nice in July by Mohamed Lahouaiej-Bouhlel, a 31-year-old Tunisian man.

Sympathisers saw they don't need a bomb or a gun to carry out slaughter on such a scale.

Here in the UK the men who murdered Fusilier Lee Rigby only needed a knife to achieve their aim.

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But the killers in that case had were known to the security services while Lahouaiej-Bouhlel had never been on the French authorities' radar.

That is partly because of the experience MI5 and the UK police have dealing with the threat of terrorism in the shape of the IRA and the work that has been put in infiltrating extremist networks both in the UK and abroad in places like Syria.

Since the 2006 London bombings Britain has managed to avoid mass attack but the police and security services believe it is only a matter of time before we have another.